I would of thought that the mileage would be stored On either the EPROM OR RAM on the cluster itself. They may be a removable on board battery which supplys power in the event of a flat battery tho I doubt it can be removed. But to have the CORRECT mileage re-entered you'll need to use the On Board Diagnostic port. (A laptop is plugged in to the ECU) This can be done via a Ford dealer or through a Mileage adjuster service. Some of these people offer the same service (Digital mileage correction)but some can be DODGY as it were. They are after all adjusting the mileage on your car which has its legality issues. This guy might be worth talking to at least and its a free phone no. http://thedashdoctor.co.uk/ Best of luck!!